Field of the Invention
The present invention relates to a method of processing data for printing (print data processing method), and more particularly, to a method of detecting white streak data occurring due to a fault in a RIP process and of correcting the same.
Description of Related Art
In a plate-making/printing system, first, an edit process using characters, parts (logo, picture, illustration, etc.) and the like constituting a print material is performed by using a computer (such as a personal computer) called a front-end, and page data describing a print target by page description language or the like is generated. Next, a RIP process is performed on the page data. In this RIP process, a rasterization process (rendering process) is performed after an interpretation process of analyzing the position or the like of each object, and multi-valued bitmap data is thereby generated, and then, halftone dot data (binary bitmap data) is generated by performing a halftone dot meshing process (screening process) on the multi-valued bitmap data. Then, a printing plate is made by a plate-making device using the halftone dot data. Thereafter, printing is performed by a printer using the printing plate. Alternatively, the halftone dot data is transmitted to a digital printer, and printing based on the halftone dot data is performed by the digital printer.
Following prior art documents are known in relation to the present invention. Japanese Laid-Open Patent Publication No. 2012-61759 discloses an invention of an image forming device which is capable of continuing printing even when an error occurs during printing. The image forming device is provided with a conversion unit configured to perform a re-RIP process based on a fixing print condition, which is a print condition for fixing an error. For example, when an error occurs due to setting of a sheet size, a re-RIP process according to the sheet size by which the error is fixed is performed, and printing is performed based on data after the re-RIP process. Furthermore, Japanese Laid-Open Patent Publication No. 2014-19016 discloses an invention of a printing system which is capable of detecting a fault occurring in an upstream process. This printing system is provided with a check unit configured to compare image data for comparison generated based on data before a RIP-process and image capturing data capturing a printing result which is based on image data for printing after the RIP process. A fault which has occurred in an upstream process is detected by the check unit extracting a difference between the image data for comparison and the image capturing data.
As described above, in a plate-making/printing system, the RIP process of performing a rasterization process on data in a vector format is performed before fabrication of a printing plate at a plate-making device or printing at a digital printer, for example. However, data of a white streak (hereinafter referred to as “white streak data”) having a width of one pixel may occur in data after the RIP process, due to various factors such as transparency effect, rotation, imposition, and the pattern of an image. For example, as indicated by an arrow 90 in FIG. 35, a part which is supposed to be painted is not painted. This part is the white streak data (note that, in FIG. 35, the width of the white part is shown with a thickness greater than one pixel for the sake of description). Occurrence of such white streak data is assumed to be caused by a fault in the RIP process.
Conventionally, such white streak data is found at the time of checking (checking by eye) of print data by a proof or the like, for example. When white streak data is found, data before the RIP process is corrected or a parameter for execution of the RIP process is changed so that the white streak data will not be included in the print data. However, since such a conventional solution results in going-back in operation processes, the operation efficiency is low. Furthermore, changing a parameter for execution of the RIP process may result in a different fault. Moreover, if white streak data is caused but the white streak data is overlooked, this results in a so-called “print accident”. It should be noted that the inventions disclosed in Japanese Laid-Open Patent Publication No. 2012-61759 and Japanese Laid-Open Patent Publication No. 2014-19016 are not aimed at detecting such white streak data. Even if a difference between pieces of data before and after RIP is detected by the printing system disclosed in Japanese Laid-Open Patent Publication No. 2014-19016, printing on a print sheet has to be performed to extract the difference, and going-back occurs in operation processes.